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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

For the fiscal year ended September 30, 2019

For the transition period from to

Commission File Number 001-32833

TransDigm Group Incorporated

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation or organization)

41-2101738

(I.R.S. Employer Identification No.)

(216) 706-2960

(Registrants’ telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes x No ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ¨ No x

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days. Yes x No ¨

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x No ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No x

The aggregate market value of the voting and non-voting common stock held by non-affiliates of the registrant as of March 31, 2019, based upon the last sale price of such voting and non-voting common stock on that date, was $24,193,750,882.

The number of shares outstanding of TransDigm Group Incorporated’s common stock, par value $.01 per share, was 53,548,349 as of November 17, 2019.

Documents incorporated by reference: Certain sections of the registrant’s definitive Proxy Statement to be filed in connection with its 2020 Annual Meeting of Shareholders, are incorporated by reference into Part III of this Annual Report on Form 10-K.

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Special Note Regarding Forward-Looking Statements

This report on Form 10-K contains forward-looking statements within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and 27A of the Securities Act of 1933, as amended. Discussions containing such forward-looking statements may be found in Items 1, 1A, 2, 3, 5, 7 and 7A hereof and elsewhere within this Report generally. In addition, when used in this Report, the words “believe,” “may,” “will,” “should,” “expect,” “intend,” “plan,” “predict,” “anticipate,” “estimate” or “continue” and other words and terms of similar meaning are intended to identify forward-looking statements. Although the Company (as defined below) believes that its plans, intentions and expectations reflected in or suggested by such forward-looking statements are reasonable, such forward-looking statements are subject to a number of risks and uncertainties that could cause actual results to differ materially from the forward-looking statements made in this Report. The more important of such risks and uncertainties are set forth under the caption “Risk Factors” and elsewhere in this Report. Many such factors are outside the control of the Company. Consequently, such forward-looking statements should be regarded solely as our current plans, estimates and beliefs. We do not undertake, and specifically decline, any obligation, to publicly release the results of any revisions to these forward-looking statements that may be made to reflect any future events or circumstances after the date of such statements or to reflect the occurrence of anticipated or unanticipated events. All forward-looking statements attributable to the Company or persons acting on its behalf are expressly qualified in their entirety by these cautionary statements.

Important factors that could cause actual results to differ materially from the forward-looking statements made in this Annual Report on Form 10-K include but are not limited to: the sensitivity of our business to the number of flight hours that our customers’ planes spend aloft and our customers’ profitability, both of which are affected by general economic conditions; future geopolitical or worldwide events; cyber-security threats and natural disasters; our reliance on certain customers; the U.S. defense budget and risks associated with being a government supplier including government audits and investigations; failure to maintain government or industry approvals; failure to complete or successfully integrate acquisitions, including our acquisition of Esterline; our indebtedness; potential environmental liabilities; liabilities arising in connection with litigation; increases in raw material costs, taxes and labor costs that cannot be recovered in product pricing; risks and costs associated with our international sales and operations; and other risk factors.

In this report, the term “TD Group” refers to TransDigm Group Incorporated, which holds all of the outstanding capital stock of TransDigm Inc. The terms “Company,” “TransDigm,” “we,” “us,” “our” and similar terms, unless the context otherwise requires, refer to TD Group, together with TransDigm Inc. and its wholly-owned and majority-owned subsidiaries for which it has a controlling interest. References to “fiscal year” mean the year ending or ended September 30. For example, “fiscal year 2019” or “fiscal 2019” means the period from October 1, 2018 to September 30, 2019.

PART I